This invention relates to the field of refrigerant-based heating and cooling systems, and to evaporative cooling systems, and more particularly to a system designed to inhibit condensation or other frozen moisture accumulation on heat exchange equipment or tubing, which tubing is typically finned, and which equipment or tubing is exposed to the air, by means of the application of a non-stick coating to the exterior portion of such air-exposed equipment or tubing, finned tubing, optional plates with refrigerant transport capillary tubes, or the like.
Virtually all heating and cooling systems utilize equipment or a heat exchange means which periodically is exposed to air containing moisture, or water vapor. For example, well-known air source heat pump systems typically utilize exterior heat exchange units consisting of finned copper tubing, which tubing transports a refrigerant such as R22,R-410A, or the like, with an electric fan utilized to blow air over the finned tubing to accelerate heat transfer from the warm air to the cold refrigerant fluid in the heating mode, and from the hot refrigerant fluid to the cool air in the cooling mode. Such a system also typically incorporates an interior air heat exchange unit comprised of finned copper tubing and an electric fan, a compressor which is used to both compress the refrigerant vapor and to circulate the refrigerant fluid through the system, an expansion valve, and other miscellaneous parts and optional apparatus, well known to those skilled in the art/field, depending on the particular design.
While copper is generally utilized for heat transfer tubing in most common refrigerant-based systems applications, other materials, such as aluminum, stainless steel, titanium or the like, may also be utilized for heat transfer tubing, just as various other system components may vary. Also, in large commercial chillers, plastic tubing is commonly utilized to transport water for evaporative cooling purposes, which water has typically been heated from waste heat augmented by heat of compression from a refrigerant-based heat transfer system.
However, when typical air-source heat pump systems are operating in the heating mode, since the refrigerant fluid, which is being circulated into the exterior outdoor heat exchange unit exposed to the air, is typically below the freezing point of water, as the exterior air temperature nears and approaches (typically about 5 degrees C. and below) the freezing point of water (0 degrees C.), humidity in the air collects on the finned tubing and is frozen. This freezing humidity gradually builds up ice accumulations to the extent that it blocks the airflow designed to pass over the finned tubing, thereby rendering the system unable to acquire sufficient heat from the air to operate at design levels. Consequently, a defrost cycle is commonly utilized to remove the ice when the accumulation becomes excessive. The defrost cycle for a residential air source heat pump system typically lasts for about eight minutes, and actually consists of operating the heat pump system in the cooling mode, so as to run hot refrigerant fluid through the exterior finned tubing to melt the ice. As the heat pump system is operating in the cooling mode during the defrost cycle, heat is being taken from the interior air via the interior heat exchange unit, which heat is typically replaced via electric resistance heat or via a fossil fuel means. This periodic defrost cycle results in excessive wear and tear on the compressor, tending to shorten compressor life, as well as in lowered system efficiencies and higher operational costs.
There have been many attempts to make the defrost cycle more efficient, such as using more efficient equipment designs, using stored energy to heat the refrigerant fluid used in the defrost cycle, and the like. However, there remains a need to provide a means to eliminate the necessity for a defrost cycle in an air source heat pump system altogether, and to eliminate unwanted ice accumulations, whether from condensation ice, freezing rain, snow, or hail, on the exterior portion of any refrigerant-based heat transfer system part, whether commercial or residential, resulting from an accumulation of frozen moisture.
Similarly, in large commercial evaporative cooling chillers, which must periodically operate in temperatures approaching or below the freezing point of water, and which sometimes must operate with a cooling load significantly less than called for by system design, the water utilized for evaporative cooling on the exterior of the heat transfer tubing may freeze. Consequently, under such conditions, there is a similar need to provide an efficient means to eliminate the necessity for a costly de-icing operation.
In Wiggs' U.S. patent application Ser. No. 10/073,515,entitled “Method and Apparatus For Inhibiting Ice Accumulation in HVAC Systems,” a new and useful method and apparatus was taught to prevent ice buildup on HVAC refrigerant/air heat exchange surfaces via coating the surfaces with a non-stick coating to which ice/frozen moisture would not adhere. While certain examples of suitable refrigerant/air heat exchange means were shown, the present invention discloses other, and potentially better, examples of refrigerant/air heat exchanger means/design which could be alternatively utilized.